JP2005530665A - Wrinkle reduction assembly - Google Patents

Abstract

An apparatus for reducing wrinkles in the membrane 102 is parallel to each other and a first pair of cylindrical rollers 100 including a first roller 108a and a second roller 108b that are juxtaposed parallel to each other and each having a substantially smooth surface. A second pair of cylindrical rollers 110 including a third roller 112a and a fourth roller 112b juxtaposed to each other, wherein at least one surface of the third roller 112a and the fourth roller 112b is provided with a chevron pattern. The first pair of rollers 108 is adjacent to and spaced apart from the second pair of cylindrical rollers 110. A method for reducing wrinkles is also disclosed herein.

Description

  The present invention relates to an apparatus and method for reducing wrinkles in membranes, particularly tubular membranes such as lay-flat tubular membranes.

  The Vertical Form Fill Seal (VFFS) packaging system has proven very useful in packaging a wide variety of food and non-food pumpable and / or flowable products. An example of such a system is the ONPACK ™ flowable food packaging system marketed by Cryovac / Sealed Air Corporation. The VFFS process is known to those skilled in the art and is described, for example, in US Pat. As described in the specification (Vogan), which is incorporated herein by reference in its entirety. In such a process, a lay flat thermoplastic film is advanced over the forming device to form a single tube, creating a vertical (vertical) fin or wrap seal, and the bottom seal is a heated seal. Made by sealing transversely across a tube with a bar. The flowable product is directed through the central vertical fill tube to the formed tubular membrane. The pouch is then completed by sealing the upper end of the tubular segment and further cutting the pouch from the tubular membrane thereon. This process can be a two-step process. That is, the creation of a transverse heat seal occurs in the first stage of the process, and then another pair of cooling / clamping means contacts the just formed transverse heat seal downstream of the first stage to cool the seal and It will be strengthened. In some VFFS processes, an upper lateral seal of the first pouch and a lower lateral seal of the subsequent pouch are made, which are cut and thereby separated between the two parts of the lateral seal. Tighten, cool and cut the seals without the need for separate steps. A commercial example of an apparatus that implements a process that further simplifies this is the ONPACK ™ 2050A VFFS packaging machine marketed by Cryovac / Sealed Air Corporation.

  In some cases, spreader fingers are used commercially in vertical form-fill-seal equipment such as the ONPACK ™ 2070A packaging machine. An example is disclosed in Research Disclosure No. 420056 published on March 20, 1999. A removable set of spreader fingers is attached to a support ring attached to the bottom end of the solid packing cylinder of the ONPACK ™ 2070A vertical form-fill-sealing machine, or preferably attached directly to the packing cylinder itself Yes. The uppermost end of the finger is configured to slide through the slot in the support ring or fill tube and through the edge of the slot guide when pivoted down into place. This supports the fingers and prevents any unwanted back and forth movement of the spreader fingers. The top end of the finger is forced against the inside of the fill tube so that the bottom end of the finger is compressed against the inside of the membrane tube as needed during part of the machine cycle. It becomes possible. The spreader fingers can be removed and replaced with different length fingers to accommodate different pouch lengths. US Pat. No. 5,038,550 (Wirsig et al.), Which is incorporated herein by reference in its entirety, is also shown in FIG. 5 in order to prepare a tubular membrane for insertion in the space between a pair of sealing jaws. The spreader finger is disclosed. These fingers are generally located above the transverse sealing assembly but below or at the lower end of the machine's fill tube area.

  For example, the pair of squeeze or discharge rollers shown in FIG. 1 and 2 of US Pat. No. 6,212,861 (Tsuruta), which is incorporated herein by reference in its entirety, also includes some VFFS. Common in equipment. These rollers generally have a smooth hard rubber or synthetic rubber surface and serve to remove fluids, fats and other food waste from the inner surface of the tubular membrane in the area where the transverse seal is to be made. . This allows the lateral seal to be made with less dirt present in the seal area, resulting in a cleaner and stronger seal. These rollers are generally located on either side of a longitudinally sealed cylinder 48 with suitable pneumatic or hydraulic means, and a pair of rollers are circulated separately from each other in a timely manner. To match the machine's pouch making cycle. The discharge roller is generally below the lower end of the longitudinal heat seal device and below the lower end of the filling tube that supplies food to the formed pouch, but above the level of the transverse seal bar Is arranged. The rollers can also be advantageous in that they help to flatten the pouch and form a bottom “stop” to allow and assist in filling the next pouch in the filling procedure.

  Thus, a typical current VFFS installation is a device having a set of spring steel spreader fingers with a set of smooth squeezing rollers below and downstream.

  It is unfortunate that the weight of the food, such as the fluid inside the pouch formed in the VFFS system, tends to wrinkle the pouch and thus wrinkle immediately after the membrane has advanced from the spreader fingers. Wrinkles can also occur if large particulates such as cubic beef are present in the vicinity of the vertical (vertical) fins or wrap seals. A smooth roller downstream of the spreader fingers does not solve the wrinkle problem.

  The presence of such wrinkles can result in defective packaging, or at least packaging that is unacceptable to membrane users and food processors. In certain applications, such as retort packaging, any wrinkles in the packaging material, particularly the sealed area of the package, are considered unacceptable. This is because low acid foods commonly packaged in the retort application field require hermetic packaging to prevent food spoilage and ensure safe food.

  The inventors have found that most of the wrinkles of the tubular membrane are removed by using a pair of chevron patterned rollers downstream of a pair of smooth rollers. As an alternative, a chevron-patterned roller can be placed upstream of a pair of smooth rollers (and downstream of the spreader fingers, if present), but the improvement in wrinkle reduction is not significant. And small.

  The present invention reduces the number of flaw wraps made in a VFFS facility by reducing the percentage of packages that have unacceptable levels of wrinkles.

  In a first aspect of the invention, an apparatus for reducing wrinkles in a membrane includes a first pair of cylindrical rollers that include a first roller and a second roller that are juxtaposed in parallel with each other and each having a substantially smooth surface. And a second pair of cylindrical rollers including a third roller and a fourth roller juxtaposed in parallel with each other, wherein a second pattern with a chevron pattern on at least one surface of the third roller and the fourth roller The first pair of cylindrical rollers is adjacent to and spaced apart from the second pair of cylindrical rollers.

  In a second aspect, a method for reducing wrinkles in a membrane includes a first pair of cylindrical rollers juxtaposed in parallel to each other, each including a first roller and a second roller each having a substantially smooth surface; A second pair of cylindrical rollers including a third roller and a fourth roller juxtaposed in parallel, wherein at least one surface of the third roller and the fourth roller is provided with a chevron pattern Providing a second pair of cylindrical rollers, the first pair of cylindrical rollers being adjacent and spaced apart from the second pair of cylindrical rollers; Advancing the membrane to contact them between the two rollers and then to pass between and in contact with the third and fourth rollers.

  In a third aspect, a method for reducing wrinkles in a membrane includes a first pair of cylindrical rollers juxtaposed in parallel to each other and each including a first roller and a second roller each having a substantially smooth surface; A second pair of cylindrical rollers including a third roller and a fourth roller juxtaposed in parallel, wherein at least one surface of the third roller and the fourth roller is provided with a chevron pattern Providing a second pair of cylindrical rollers, the first pair of cylindrical rollers being adjacent and spaced apart from the second pair of cylindrical rollers; Advancing the membrane in contact with the four rollers and then passing between the first and second rollers in contact therewith.

  The present invention is illustrated with reference to the accompanying drawings, which include various views of various embodiments of the invention.

  FIG. 1 shows a prior art vertical form-fill-seal device that can be used with the device and method according to the present invention. The vertical form-fill-seal device 40 is schematically illustrated. The apparatus 40 uses the multilayer layflat film 41 as a roll stock. A product 42, such as cubic beef or other food or non-food, especially a pumpable product, is supplied to the device 40 from a source (not shown) manually or by machine, and a predetermined amount of product from the source. 42 passes through the funnel 43 to the upper end of the forming tube 44 or to other conventional means. The packaging is formed in the lower part of the apparatus 40, and a flexible film 41, which is a raw material for forming the packaging, is fed from a feeding roll 51 on several forming bars (not shown), and a forming cylinder 44 is formed. Wrapped around (often referred to as a “sailor collar” or “former collar”), a longitudinal seal 47 is provided by a longitudinal heat seal device 46, resulting in a vertically oriented tube 48. The transverse heat seal bar 45 serves to close and seal the bottom end of the vertically sealed cylinder 48 in the horizontal direction to form a pouch 50, which is immediately filled with the product 42. A membrane drive belt 52, powered and directed by a roller, advances the tube 48 and the pouch 50 by a predetermined distance, as shown, after which the end seal bar 45 is vertically sealed with the pouch 48. Close across the lower end of the pouch 49 and simultaneously seal horizontally, as well as across the top end of the sealed pouch 49 and simultaneously horizontally sealed to form a product packed in the sealed pouch 49. The next pouch 50 is then filled and advanced with the weighed amount of product 42 and the packaging cycle is repeated. It is also conventional to incorporate a cut-off knife (not shown) into the end seal bar that serves to cut the lower sealed pouch 49 from the bottom of the upstream pouch 50.

  FIG. 2 is a schematic perspective view of the apparatus 100 of the present invention. A layflat tubular membrane 102, such as a tubular membrane made by the VFFS process described above and having a longitudinal seal 104, is advanced between a pair of discharge rollers 106 in the direction indicated by the arrow, and then a pair of It is advanced between the rollers 110 with the chevron pattern.

  The pair of discharge rollers 106 includes a first roller 108a and a second roller 108b. These rollers function to remove fat, liquids, and other materials from the inner surface of the membrane 102 in preparation for the lateral heat sealing step as described herein. Means (not shown), such as a discharge roller assembly, are well known to those skilled in the art, but this includes rollers 108a and 108b in an "open" position where the rollers are separated from each other and the membrane, and rollers 108a and 108b. 108b is reciprocated from a “closed” position that presses on the respective outer surface of the membrane 102 to achieve the release function. Such means include pneumatic or hydraulic means synchronized to the machine packaging cycle by suitable timing means for swinging or advancing each roller between an open position and a closed position. Electromechanical means such as linear actuators or servomotors on mechanical links can also be used to actuate the movement of the discharge and chevron rollers. For example, suitable bearing blocks are used in conventional equipment to provide relative movement and support for the discharge roller. The roller itself will have a journal center on which support means (not shown) will support the roller and each roller will move in the direction indicated by the arrow when in contact with the advancing membrane 102. Allows free rotation about the axis of the.

  The pair of chevron-patterned rollers 110 includes a first roller 112a and a second roller 112b. These rollers have been found to function to remove wrinkles generated in the layflat tubular membrane 102 during the VFFS process. Means similar to those used for the discharge roller 106 include rollers 112a and 112b in the "open" position where the rollers are separated from each other and the membrane, and rollers 112a and 112b on the respective outer surface of the membrane 102. It can be used to achieve a wrinkle removal function by reciprocating from the “closed” position of pressing. Such means include pneumatic or hydraulic means synchronized to the machine packaging cycle by suitable timing means for swinging or advancing each roller between an open position and a closed position. The roller itself will have a journal center on which support means (not shown) will support the roller and each roller will move in the direction indicated by the arrow when in contact with the advancing membrane 102. Allows free rotation about the axis of the.

  FIG. 3 is a plan view of a pair of chevron patterned rollers 212a and 212b according to the present invention when looking down from above. The discharge roller is not shown for the sake of clarity. Each of the two rollers has a chevron pattern defined by a series of lands 218 and grooves 220 arranged in alternating order along the length of each roller. These lands and grooves form a spiral pattern across the rollers, and the wrinkles formed on the film are removed as the film passes between the rollers. The visual effect of looking at the operating roller from the perspective of FIG. 3 is that the land and groove pattern moves toward the outer end of each respective roller. Thus, as the membrane 202 moves inward relative to the drawing as shown in FIG. 3, the chevron rollers 212a and 212b each rotate in a direction toward the longitudinal centerline of the view defined by the membrane 202. .

  FIG. 4 is a cross-sectional view of a portion of a chevron patterned single roller of the present invention. Roller 312 a shows a series of alternating lands 318 and grooves 320. In one preferred embodiment, the land is relatively flat on its outer surface to achieve smooth and uniform contact with the layflat film. The groove is shown as asymmetric, i.e., the side of the groove facing toward the middle line 330 of the roller is relatively flat, but the side toward the lateral end of the roller is curved. This is the preferred embodiment, but any suitable profile of the lands and grooves will thereby allow the film to pass between a pair of chevron patterned rollers if they are not used. It is contemplated if it results in fewer wrinkles present in the membrane. The outer portion 316 of the cylindrical roller can be made of any suitable material. Preference is given to natural rubber or synthetic rubber. The hollow cylindrical core 340 can be made of any suitable material. Preferred are relatively rigid and strong materials such as metals, especially steel or aluminum or hard plastics. The roller 312a has a hollow core 314 to accommodate a rod or bearing to facilitate rotation and support of the roller.

  FIG. 5 is a side view of the apparatus of the present invention. The layflat tubular membrane 406 passes between a pair of discharge rollers 402a and 402b and a pair of chevron patterned rollers 404a and 404b. The spreader fingers 400 form part of a pair of spreader fingers (the other not shown for clarity) that serve to spread the tubular film before it reaches the discharge roller 402. The direction of the membrane 406 is indicated by an arrow.

  FIG. 6 is a perspective view of a prior art subassembly 510 into which the apparatus of the present invention can be mounted. In the drawing, the chain 520 drives the discharge roller assembly 530. One discharge roller 540 of a representative roller pair is shown. The arms 550 and 560 may be circulated back and forth from each other by suitable means (not shown for clarity) such as pneumatic or hydraulic cylinders, or servo motors or other mechanical linear actuators. it can. For purposes of the present invention, arms 550 and 560 can be extended downward to accommodate a pair of chevron-patterned rollers, as best seen in FIG.

  Although the present invention has been described in particular as having a pair of chevron-patterned rollers downstream (typically below) a pair of discharge rollers, the reverse arrangement can also provide some benefit. it can. Thus, a pair of chevron patterned rollers in a VFFS system can be placed upstream of the pair of discharge rollers (generally above).

  One skilled in the art will also appreciate that after reviewing this specification, multiple pairs of either discharge rollers or chevron rollers can be used in series. That is, in an alternative embodiment, the membrane can be passed sequentially through a pair of chevron patterned rollers, then a pair of discharge rollers, and yet another pair of chevron patterned rollers.

  In yet another embodiment, when the present invention is used in a packaging system in which the discharge roller and the chevron are not planar, i.e. the advancing membrane does not move linearly in the space between the discharge roller and the chevron. The intermediate roller such as a dancer roller can be disposed between the discharge roller and the angle roller.

  The apparatus and process according to the present invention can be carried out with any suitable membrane, preferred are thermoplastic polymer membranes such as those designed for VFFS applications. An example of this is the FS7055 (TM) membrane sold by Cryovac / Sealed Air Corporation. The membrane is preferably sealed at the lowest possible temperature and a relatively strong seal is produced at this temperature. Generally, the membrane is sealed at a temperature from about 150 ° C to 210 ° C.

  The apparatus and process of the present invention can be used to package pumpable products, particularly food products.

  During use, the pressure on the chevron patterned rubber roller set as well as the discharge roller can be adjusted by suitable means.

  This package can be manufactured by a continuous or intermittent VFFS pouch manufacturing process.

  In the test, an ONPACK ™ 2070B vertical form-fill-seal machine was installed and operated on cubic beef containing salt water using two retort grade thermoplastic membranes. The first film was transparent and the second film was white opaque. End seal wrinkles are common in retort grade packaging applications and the intention to remove these wrinkles has not been successful. To correct this wrinkle problem, a pair of chevron-patterned rollers (rollers with a spiral pattern cut into the surface running from the middle of the roller toward each of the two respective lateral edges of the roller ) Was installed on the 2070B facility with new bracket means and drive chain, and the new roller was mounted vertically above a pair of discharge rollers with a smooth surface and separated from the discharge roller. The chevron patterned rollers were driven passively. That is, the angle roller did not supply the starting force to advance the membrane. The smooth discharge roller was driven to provide the starting force to advance the membrane. The degree of pressure exerted by the chevron roller on the membrane passing between the rollers when the rollers come together and contact the membrane passing between them is useful for correct membrane progression I understood.

  When the test membrane is moved, the profile of the chevron patterned roller, which is vertically above the driven flat squeeze roller, contributes somewhat to reduce wrinkling in the membrane and final packaging, but greatly contributes. I found out that I would not. A pair of spreader fingers was also placed above the angle roller. It has been found that the distance between spreader fingers (305-310 mm) appears to be an important parameter in reducing wrinkle frequency and severity.

  A test similar to that of Example 1 was performed, but in this case the rollers were repositioned and a pair of smooth discharge rollers were placed above the pair of chevron-patterned rollers. Also in this test, the chevron patterned roller was driven and the smooth discharge roller was passive. Furthermore, the discharge rollers were not in contact with each other in the closed state (no film was present between the rollers). This is because the angle of the chevron roller is much larger than the diameter of the discharge roller. The discharge rollers do not come into contact with each other and therefore do not exert a great pressure on the membrane passing between the rollers, and the seal discharge by the discharge roller (from the inner surface of the tubular membrane in the vicinity of the membrane to be sealed laterally) The removal of residual product) was incomplete.

  Nonetheless, when the test membrane was moved, the generation of wrinkles was still unacceptable, but the incidence of wrinkles decreased. It has also been confirmed that the distance between spreader fingers appears to be an important parameter in reducing the frequency and severity of wrinkles.

  A roast of meat around the neck of the cow was purchased and sliced into cubic shapes. These cubic meats were cooked in boiling water for about 30 minutes to the same level of firmness as the previous test.

  ONPACK is a pair of chevron-patterned rollers that have a stronger pattern (steep angles where the land and groove directions form a smaller angle with the longitudinal axis of the roller) on each lateral half of the roller. It was installed on the (trademark) 2070 machine at a position vertically below the pair of smooth surface discharge rollers. The chevron patterned roller was chain driven while the discharge roller was passive.

  A new bracket means has been made for two pairs of rollers, which allows the discharge rollers to contact each other when there is no film passing between them, as the film travels on the rollers and thus at various levels Of pressure could be applied to the membrane. This system significantly reduced the incidence of seal wrinkles compared to the same profile where the discharge roller did not contact.

  Increasing the pressure on the chevron roller also had a noticeable effect in reducing wrinkles compared to a relatively low pressure. There were 69 packages in a row, but there were no end seal wrinkles.

  The spreader fingers in this particular configuration were bent to a distance of 280 mm (from 305 mm), but the package still did not wrinkle.

  It should be understood that variations and modifications of the present invention can be made without departing from the scope of the invention.

  For example, in an alternative embodiment, a chevron patterned roller can be paired with a smooth surface roller. For example, the roller 108a is paired with the roller 112b. Such a combination has been found to reduce wrinkles in the single wound membrane passing between the rollers and is expected to provide some improvement when reducing wrinkles in the layflat tubular membrane. This alternative combination is implemented in combination with a pair of smooth discharge rollers located upstream or downstream of an alternative chevron / smooth roller combination.

  The present invention has been described herein primarily with reference to a pair of smooth rollers that are vertically spaced apart from a pair of chevron patterned rollers or pairs of chevron and smooth rollers. It will be appreciated that these respective roller pairs can have any suitable angle or position relative to each other and can belong to and be placed in any plane ranging from vertical to horizontal.

  Similarly, any suitable chevron pattern with various groove depths, adjacent land spacings, land widths, and angles or pitches of the helical configuration in each lateral half of the chevron patterned roller can be used between the roller pairs. It can be used as appropriate and effective in achieving some wrinkle reduction in the membrane passing through. The horizontal spacing between the lands does not necessarily have to be constant, so the overall pattern on each side or side half of the roller does not have to be exactly hung, and the two roller The angle may be changed up to each outer lateral edge. One or more lateral portions of the chevron patterned roller can be smooth, if appropriate, so that the chevron pattern appears in one or more bands on the roller.

  The present invention relates to wet flowable and / or pumped fluids, including low viscosity fluids (eg juices and carbonated beverages), high viscosity fluids (eg seasonings and sauces), fluid / solid mixtures (eg soups), gels, etc. Can be used to package possible products. Chemical fertilizers, engine oils, engine additives, dry or wet cosmetics, drugs, drug powders such as foot powder and talc powder, non-food products such as sand and cement can also be advantageously packaged with the pouch of the present invention. The present invention finds particular application in the packaging of dry flowable and / or pumpable products. These include very finely separated or finely ground products such as flour and cake mixes, somewhat coarser products such as spices and sugar, and more coarse products such as rice and breakfast cereals. Products with large grains, such as pet food, and non-food dry flowable and / or pumpable products can be advantageously packaged.

  As used herein, “membrane” means either a multilayer or a single layer of films, laminates, and webs that may be used in connection with the present invention. An FS laminate, such as FS7055 ™, marketed by Sealed Air Corporation through its Cryovac Division, is an example of a suitable packaging material for the VFFS process. These laminates are described, for example, in US Pat. No. 4,746,562 (Fant), which is incorporated herein by reference in its entirety.

There is another laminate based on the SCLAIR ™ sealant membrane, which is marketed by DuPont Canada, for example as described in US Pat. No. 4,521,437 (Storms), which is incorporated herein by reference in its entirety. Ethylene / alpha-olefin copolymer. A commercial monolayer from DuPont Canada is FS-3. A commercial multilayer laminate is CL303. Many other membranes and laminates useful for dry or wet fluid packaging are available and can be used advantageously in the present invention.
The present invention can be used in combination with or as a subsystem of various equipment systems. Preferred end uses are in the VFFS application field for use in commercial equipment such as ONPACK ™ 2070, 2002, and 2050VFFS packaging equipment. However, those skilled in the art will appreciate that wrinkle reduction is a desired function, whether for packaging or simply for advancing the membrane, for example in a roll, to use the invention in other equipment. It will be understood.

1 is an elevational view of a prior art vertical forming, filling and sealing device for creating a pouch from a layflat rollstock film. FIG. It is a schematic perspective view of the apparatus of this invention. It is a top view of a pair of roller by which the angle pattern was given of the present invention. FIG. 3 is a cross-sectional view of a portion of a chevron patterned roller of the present invention. It is a side view of the apparatus of this invention. 1 is a perspective view of a prior art subassembly in which the apparatus of the present invention can be mounted. FIG.

Claims (21)

a) i) a first roller and ii) a second roller, wherein the first and second rollers are juxtaposed parallel to each other, each having a substantially smooth surface;
b) i) a third roller and ii) a fourth roller, wherein the third and fourth rollers are juxtaposed in parallel with each other, and at least one of the third roller and the fourth roller has a chevron pattern on its surface A second pair of cylindrical rollers
An apparatus for reducing wrinkles in a membrane,
The first pair of cylindrical rollers is adjacent to and spaced apart from the second pair of cylindrical rollers.   The apparatus of claim 1 wherein the first and second rollers and the third and fourth rollers are rotatable about their respective axes.   The apparatus of claim 1, wherein the first and second rollers have smooth outer surfaces.   The apparatus of claim 3, wherein the outer surfaces of the first and second rollers are constructed from natural or synthetic rubber.   The apparatus of claim 1, wherein the first and second rollers are located above the third and fourth rollers.   The apparatus of claim 1, wherein the third and fourth rollers are located above the first and second rollers.   The apparatus of claim 1, wherein the first and second rollers and the third and fourth rollers are adapted to receive passage of a layflat membrane in contact with these rollers.   The apparatus of claim 1, wherein the first and second rollers and the third and fourth rollers are adapted to circulate between an open position and a closed position.   The apparatus of claim 1, wherein at least one of the third and fourth rollers includes a series of lands and grooves alternating on the surface thereof.   The apparatus of claim 1, wherein the third and fourth rollers are adapted to receive a layflat membrane that passes between and is in contact with the rollers to reduce wrinkles present in the membrane.   The apparatus of claim 1, wherein a chevron pattern is disposed on the surface of each of the third and fourth rollers. a) i) (a) a first roller and (b) a second roller, the first and second rollers juxtaposed parallel to each other, each having a substantially smooth surface, a first pair of cylinders Laura,
ii) includes (a) a third roller and (b) a fourth roller, wherein the third and fourth rollers are juxtaposed in parallel with each other, and at least one of the third roller and the fourth roller has a chevron pattern on the surface thereof Has been placed,
The first pair of cylindrical rollers is adjacent to and spaced apart from the second pair of cylindrical rollers;
Providing a second pair of cylindrical rollers;
b) advancing the tubular membrane such that the membrane first contacts them between the first and second rollers and then passes between and in contact with the third and fourth rollers And a method for reducing wrinkles in a membrane.   13. The method of claim 12, wherein the first and second rollers and the third and fourth rollers are rotatable about their respective axes.   The membrane is advanced in a straight line so that the membrane first contacts and passes between the first and second rollers and then passes between and between the third and fourth rollers. Item 13. The method according to Item 12.   13. The method of claim 12, wherein wrinkles in the film are reduced as the film passes between the third and fourth rollers.   The method of claim 12, wherein a chevron pattern is disposed on the surface of each of the third and fourth rollers. a) i) (a) a first roller and (b) a second roller, the first and second rollers juxtaposed parallel to each other, each having a substantially smooth surface, a first pair of cylinders Laura,
ii) includes (a) a third roller and (b) a fourth roller, wherein the third and fourth rollers are juxtaposed in parallel with each other, and at least one of the third roller and the fourth roller has a chevron pattern on the surface thereof Has been placed,
The first pair of cylindrical rollers is adjacent to and spaced apart from the second pair of cylindrical rollers;
Providing a second pair of cylindrical rollers;
b) advancing the tubular membrane such that the membrane first contacts them between the third roller and the fourth roller and then passes between the first roller and the second roller in contact therewith And a method for reducing wrinkles in a membrane.   The method of claim 17, wherein the third and fourth rollers and the first and second rollers are rotatable about their respective axes.   The membrane is advanced in a straight line such that the membrane first contacts and passes between the third and fourth rollers and then passes between and in contact with the first and second rollers. Item 18. The method according to Item 17.   18. The method of claim 17, wherein wrinkles in the film are reduced as the film passes between the third and fourth rollers.   The method of claim 17, wherein a chevron pattern is disposed on the surface of each of the third and fourth rollers.

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